Mary Renault takes the Greek Legend of Theseus and the Minotaur; combines it with real architectural findings; adds in her own literary skill.. and makes it bigger and better in the telling.
My own telling of the Theseus legend would mostl likely cover half a page. Renault has made it a 350 page adventure that is half historical-fiction and half swords and sorcery fantasy.
The style of thing reminds me a fair bit of Michael Moorcock's Elric series. It's not the ending that counts here, and its not about happily ever after (sorry), it's more of a series of adventures that you can just enjoy for what they are, and then let the hero ride off into the sunset.
I thought it was pretty cool, tho I won't recommend it for everyone. I hope to get onto some of her other books someday, they just happen to be not high enough on my tbr pile.